Boilermakers and boilermaker mechanics construct, assemble, and repair boilers, vats, tanks, and other large metal vessels that are designed to hold liquids and gases. Following blueprints, they lay out, cut, fit, bolt, weld, and rivet together heavy metal plates, boiler tubes, and castings. Boilermaker mechanics maintain and repair boilers and other vessels made by boilermakers. There are approximately 17,210 boilermakers working in the United States.